Ion milling apparatuses are installed with a sample in a vacuum exhausted sample camber, irradiates the sample with an argon ion beam applied with a voltage of approximately 10 kV or less without focusing, sputters atoms from a sample surface utilizing physical sputtering phenomenon, and polishes the sample surface without applying stress thereto. The ion milling apparatuses are used when a sample for a scanning electron microscope (SEM) or a transmission electron microscopy (TEM) is produced.
For example PTL 1 discloses an ion milling apparatus including a blocking plate (mask) formed by a material having a low sputtering yield (material which is not abrased even when an ion beam hits the material). This blocking plate (mask) blocks a part of a sample excluding an exposed part from an ion beam while exposing the part of the sample from an end surface of the blocking plate by approximately 50 to 200 μm. That is, performing ion beam irradiation while the sample is partially exposed results in processing of the sample into a shape corresponding to the end surface of the blocking plate.